At least 37 killed in airstrikes on a busy market in rebel-held Syrian town

At least 37 people have been killed in airstrikes on a busy market in a rebel-held town in northwestern Syria, according to opposition activists and a war monitor.

More than 100 others were injured in the attacks in Maaret al-Numan in southern Idlib province, which caused widespread destruction and buried several people under the rubble.

The Britain-based Syrian Observatory for Human Rights called it the largest single death toll since a Russian-Turkish truce collapsed in late April - and said the dead included two children.

The Observatory, which monitors the fighting on the ground in Syria through a network of activists, added that the number of deaths was likely to rise because of the large number of wounded.

Hours after the airstrikes, paramedics were able to remove a child alive from the rubble.

Russian warplanes are being blamed for Monday's strikes, but Russia's Defence Ministry denied the reports, dismissing them as a "hoax".

Shortly afterwards, state media said rebels shelled a government-held village, killing seven people.

A member of the Syrian Civil Defence, also known as White Helmets, said one of their colleagues was killed in a second airstrike that hit the market.

The war in Syria has been raging since 2011 and at its height, various rebel groups - including ISIS - held as much as a third of the country.

That has now shrunk - and there are just a few remaining pockets of resistance.

The most significant is in Idlib province in the north - and around three months ago the regime launched a major offensive to retake it.

Since then, an estimated 750 civilians have been killed - many of them in schools, hospitals and residential areas.

The bombardment has intensified dramatically in the last 2 days, with around 75 people killed in the last 24 hours alone.

Dominated by al Qaeda-linked militants and other jihadi groups, Idlib province and northern parts of the nearby Hama region are the last major rebel stronghold in the country outside the control of Syrian President Bashar Assad.

Despite the heavy bombardment, Assad's forces have been unable to make any significant advances.

Militant groups have hit back hard, killing an average of more than a dozen soldiers and allied militiamen per day in recent weeks.

The fighting has killed more than 2,000 people and displaced hundreds of thousands.